Recently noticed on the 'rex' variety on the Buttercrunch lettuce. An obvious yellowing of the crop.
Pre-empt allows you not to adjust pH given the organic base of the crop. I ended up testing and came up with 8.0 and was able to bring it down to 6.1 on the meter.
We will see if this updates. Looks like we are about 10-12 days into the crop with a goal of 28!
This is our 2ND set in Zone C. Zone B and Zone A are still in the 'nursery' phase of the plugs. They also had a high pH that was adjusted. However there were no signs of nutrient deficiency.